Self-synchronizing television system



April 16, 1946. .1. H. HOMRIGHOUS SYNCHRONIZING TELEVISION. SYSTEM SELF- 2 Sheets-Sheet 1 Filed July 21, 1942 FIG! April 16, 1946.

J. H. HOMRIGHOUS SELF-SYNGHRONIZING TELEVIS ION SYSTEM 2 Sheets-Sheet 2 Filed July 21, 1942 RF. I VIDEO 25a POWER AMP. DET. LP. DH 'AMP.

Patented Apr. 16, 1946 UNITED sr TENT Fries I 2,398,641 SELF-SYNCHRONIZING TELEVISION SYSTEM 48 Claims.

My invention relates to new and useful improvements in synchronizing the scanning devices used in television, and particularly, a synchronizing system wherein the control signals are transmitted irom the transmitter to the receiver during the interval between lines and fields.

Accordingly, one of the main objects of my invention is the provision of means for developing synchronising or control signals, during the interval between the scanned lines in a field and between the picture fields for controlling the scanning action at the transmitter, and to modulate the carrier with the developed synchronizing or control signals, during the interval between scanned lines and picture fields to thereby govern the scanning action at the receiver.

Another main object of my invention is the self synchronizing feature at the receiver, whereby the line scannin is almost instantly synchronized with the transmitter when placed in service, or after an interruption from fading signals.

Another object is the provision of means for adjusting the number of lines per field, over a wide range.

Another object is the provision of means for adjusting the number of frames in a given time, so that a wide range in the number of pictures per second may be obtained.

Another object of my invention is the provision of means, whereby the receivermay be used for monitoring a television broadcast of any number of pictures per second, and any number of lines I per picture, regardless of the type of synchronizing signals used.

Another object of my invention is the provision of means for assuring the continual deflection of the cathode ray beam in the absence of transmitted signals.

Another object of my invention is the provision of means at the receiver for returning the cathode ray to its starting point from any location in the picture.

Another object of my invention is the provision of a new and improved cathode ray tube to initiate the line and frame cut ofi impulses.

Another object is the provision of an auxiliary cathode ray tube for reproducing the blanking signals as white instead of black and for utilizing the light from this source for controllin the scanning and framing actions.

Several methods for developing and transmit ting control frequencies have been devised; for instance, control frequencies have been developed by tuned circuits and transmitted separately from the video frequencies either as a separate modulation on a separate carrier, or in the interval between successive picture fields. In my prior application Serial #306,537, filed Nov. 28, 1939,,

Patent No. 2,309,393 issued Jan. 26, 1943, control signals are combined with the picture signals in such manner that both are transmitted and reproduced as picture or video signals.

In my present invention, single impulses or control signals are developed at the end of each line and at the end of each picture field, and these signals are modulated on the carrier during the interval between lines and the interval betwen picture fields to control horizontal and vertical scanning action at the receiving station. These signals are applied at the receiving station to trigger or stop the forward deflection of the oathode ray.

This synchronizing system may be known as the Follow up System, that is, the receiver is notdriven into synchronism but follows the various movements of the transmitter in unison; also, since no tuned circuits are used in developing synchronizing signals this system is very flexible and will respond to a wide range in the number of lines per picture and also a wide range in the Figure 5 is a diagrammatic view of the horizontal and vertical deflecting apparatus illustrated in Figure 4.

In Figure 1, the numeral I designates a cathode ray scanning device or transmitting tube of conventional type, and is known as an Iconoscope," and as illustrated it comprises a mosaic 2, photoelectric screen on which a light image of the object is projected and an electron gun for generating a ray of electrons directed at the screen, and two sets of deflecting plates for deflecting the electron ray at the line and field frequencies, so that it is caused to scan the screen. The picture is thereby developed and fed by an output connector 3 to a modulating amplifier d.

A carrier Wave is provided by an oscillator 5.

In the power amplifier I this carrier wave is modulated by the frequency band video or picture signals and also by synchronizing impulses from the horizontal deflecting apparatus I and the vertical deflecting apparatus il between the horizontal lines and between image fields through the modulation amplifier 4. The signals from the amplifier I are supplied by a connection 1 to the antenna 8.

The control or synchronizing signals and the video signals are transmitted on the same carrier. Sound signals may be transmitted on a separate carrier or they may be transmitted as video signals as shown in my above mentioned prior application.

With reference to Figure 2 the apparatus for horizontal deflection comprises a condenser ll charged through an adjustableresistance II from a positive potential source as indicated. 81/ movement of the switches II and I4, other condensers l5 and it may be charged through re- -sistances l1 and It respectively from a high positive potential source to supply different predetermined line frequencies for horizontal deflection. Charging current control may also be obtained by varying the resistances through movable contacts I! or 20 or 2|, to give close frequency adjustments.

When the voltage across condenser II, II or it builds up, depending upon which switch contacts are closed, the saw tooth voltage wave in the plate circuit of tube 22 is impressed 0n the grid 23 of double purpose tube 24 through the voltage dividing resistance and a slidable contact 25 for controlling the amplitude of the saw tooth voltage wave. The output of push-pull amplifier tube '24 is applied to the load resistors 28 and 21 to alter the potential on the horizontal defleeting plates 28 and 29 of'tube I to effect in a well known manner the forward movement of the cathode ray.

To initiate the discharge of condenser II, I!

or it I provide a scanning device or cathode ray tube 30 of conventional type except that it may be of small size, and it may comprise a fluorescence screen or target ll of rectangular shape, and an electron gun for developing a ray of electrons directed toward the screen. The control electrode of this tube is biased to furnish a constant intensity electron ray. Only one set of electrostatic plates 32 and 33 may be furnished to deflect the electron ray in a forward and backward direction. A small photoelectric cell 34 in a separate glass tube is provided near one edge of the screen. This photo-electric tube may be coated with fluorescence material of rather fast decay.

The plates 32 and 33 are multipled to the plates 28 and 29 of tube I so that the cathode ray in both tubes travel across their respective screens in synchronism. However, should it be desirable tojcenter the electron ray of tube 30 slightly of! side, then a separate set of feeders for the deflecting plates should be provided from the load resistances 2t and 21.

When the cathode ray of tube 30 arrives at the edge of the screen having the photocell 34, the change of light in this cell. due to the fluorescence material, will cause a voltage pulse to be applied to the grid 35 of the double triode tube 38. This tube causes three things to occur; first, the signal is amplified in th plate circuit and is then applied to the primary winding 31 of the blanking transformer through resistance 38 and conductor 39 for extinguishing the cathode 1'9 during its backward movement; second, this same signal is applied through resistance 40 to the grid of tube 22 and amplified in its plate circuit and applied through coupling condenser 4| to the grid of modulation amplifier 4 for modulating the carrier with a positive high potential impulse during retrace as illustrated at 42 in Figure 3; third, the signal is applied in opposite phase to the second grid of tube II and amplifled in its plate circuit and then applied through resistance 43 to the grid 44 of the trigger tube 22. This tube then becomes conductive to discharge either of the connected condensers II, II or I6.

From the foregoing it will be understood that the photocell 34 causes the cut oil orhorizontal return trace of the cathode ray, and'modulates the carrier with a positive pulse between lines and also extinguishes the electron beam, and furthermore, line frequency may be varied to meet any operating condition.

With further reference to Figure 2. the vertical deflecting apparatus II is quite similar to the deflection apparatus I, and comprises a condenser 45, charged through an adjustable resistance 48 from a positive potential source as indicated. By rotating the switches 41 and 4! other condensers 4t and 50 may be charged through resistances ll and 52 respectively from a high positive potential source to supply different predetermined frame or picture frequencies. Charging current control may be also obtained by varying the resistance through movable contacts ll, 84 or II, to give close framing frequency adjustments.

When the voltage across any one of the condensers 45, 49 or 50 builds up the saw tooth wave in the plate circuit of tube It is impressed on the grid 51 of tube It through the voltage divider resistance and movable contact 5! for controlling the amplitude of the saw tooth voltage wave. The output of the push-pull amplifier tube 58 is applied to the load resistors I and "A to alter the potential on the vertical deflecting plates ti and 62 of tube l' to effect the forward movement of the electron ray.

To initiate the discharge of condensers 4!, 40, or 50, I provided a scanning device or cathode ray tube 63 of conventional type and exactly like tube 30 previously described having a screen or target 84 and photo-electric cell 85.

The plates 56 and 61 are multipled to the vertical deflecting plates BI and 62, respectively, so that the vertical movement of the electron rays across theirrespective screens will be in synchronism.

When the cathode ray of tube 63 arrives at the edge of the screen having the photocell II, the change of light caused by the electron ray impinging the fluorescence material will cause a voltage wave to be applied to the grid 89 of the double triode Hi. This tube will initiate three conditions; first, the signal is amplified in the ing apparatus 8 to cause, as previously explained.

the return of the electron ray to its horizontal starting position, extinguishing the electron ray in tube i and modulating the carrier with a positive high potential in the same phase relation as the impulse from tube it. The modulation of the carrier with two positive pulses of high potential in phase will produce a greater amplitude than either would alone, as illustrated at 1B Figure 3.

The third condition is that the signal as applied to the second grid of tube is amplified in its plate ,circuit and applied through resistance 18 to the grid of the trigger tube 56. This tube then becomes conductive to discharge the connected condenser 65, 69 or 50.

With certain types of pick up tubes such as that shown at i it may be necessary to make corrections in the horizontal deflection for the "Keystone effect and in order to do this I pro.- vide an auxiliary push-pull amplifier tube '79, having a control grid 80, connected to grid 23 of amplifier 2%. The plate circuits of this tube are connected to load resistances not shown but similar to 26 and 21. Theme. to the deflecting plates vertical retrace period from the second plate cire 28 and 29 of tube l instead of the conductors shown in multiple with the plates. 32 and 33. so that the horizontal deflection of tube 5 may be deflected through a changing angle rather than the constant angle of deflection for tube 30. This tube 19 is also provided with a screen grid dl connected by conductor 82 to the load resistor 60 for varying the potential on the horizontal defleeting plates of tube i in accordance w the field deflection.

From the foregoing it will be understood that the photo-cell 85 causes the return of the electron ray both vertically and horizontally to its starting point, modulates the carrier with a positive high potential pulse between fields or picture frames and also extinguishes the electron beam of tube I, all during the retrace period. Furthermore, line and frame frequency may be varied to meet any operating condition such as 24 or 30 pictures per second, etc. By observing the sweep or otherwise timing the cathode ray in tube 63 it may be adjusted through the variable resistances 45, 5| or 52 and different condensers 35, $9 or 50 to operate at a particular frequency while the amplitude may be adjusted at contact 59 to cut off vertical deflection at any desired number of lines per field.

The mosaic, or screen 2, in Figure 1 may have separate strips of metal, such as aluminum, at the leaving edges for the cathode ray as illustrated at 83 and 86. These strips are shown for clearness on the right side and on the bottom of the mosaic, but due to the lens system of the pick up tube I, the location of the metal strips may be reversed. Y

Separate leads may be brought out through the glass tube from these metal strips 83 and M, such as the lead 85 and connected to the horizontal and vertical deflecting apparatus at 86 and 87 respectively thus replacing the photocells 3d and E5 and also eliminating the tubes 36 and 63.

The operation is as follows: The electron ray is deflected beyond the leaving edges of the mosaic 2 and impinge the plates 83 and 85 to impress an E. M. F. on the tubes 36 and lo. These tubes will operate, as before described, to effect horizontal and vertical scanning actions.

It is to be understood that the photocells 3d and 65 may be placed inside of tube I near the cathode ray leaving edge of the mosaic and located as illustrated for the metal plates 83 and 84. These photocells would be coated with fluorescence material of fast decay, thus eliminating &

tubes 89 and at. The operation would be as previously described.

To provide interlace scanning, where the lines starting point which will cause the electron my to travel in, almost a straight line during retrace instead of backward and forward across the image screen.

In order to accomplish the above method of interlace, where the number of lines per frame and the number of frames per second may be varied as desired. I employ a double coil toggle action relay 88, which is operated during each cult of tube over conductor as, contacts so, coil at to battery thus momentarily energizing the coil 9! to pull armature toward its pole piece where it. will remain until coil 93 is again energized. The energization of coil til closes the springs 92 to coil 98, and opens the springs and the springs 96. The opening of spring contacts opens the circuit to the dash pot relay 95 which will release to open its springs 98, thus breaking the circuit through the primary winding Qftransmrmer bl which supplies a negative pulse to the grid of the line trigger tube 83 over conductor 98. This negative pulse will have no effect on tube 35. However, the next field control pulse will energize the coil 93 and the armature will be attracted to its pole piece, as shown in the drawings, closing contacts 9% which will energize the slow pull up dash pot relay as, causing a positive pulse to be applied to the tube 36, thus returning the electron my to its starting point. Therefore every other field control pulse will cause the horizontal deflection to be stopped and the ray returned to its starting point. The timing device 95 is adjusted to return the electron ray to its starting point at the half way point onthe first line in every other field. Therefore it will be understoodfrom the above that the interlace action is positively controlled at the start of each fieldrather than depending upon the duration of the retrace period after ending the field scanning with a fraction of a line. The switch 99 may be opened for progressive scanning.

With reference'to Figure 4, showing a receiving station, the antenna Ebb receives the carrier signals from the transmitter antenna 8 to a radio frequency amplifier lili. An oscillator H02 reacts with these signals in the first detector stage 8 E13 on the supcrheterodyne principle to produce an intermediate frequency which is supplied to the video intermediate'frequency stage it. After suitable amplification the videosignal and the control signals are detected at 15 and applied to the power amplifier I05 and after amplification in this tube they are applied to a scanning device llll. The device iblis represented a being in the form ofa cathoderay tube of a conventional type and comprises a fluorescence screen control electrode of the electron gun, whereby, the

intensity of the electron ray is made to vary with the video or picture signals. The horizontal deflecting apparatus use receives the line synchronizing impulses from the second detector output and the vertical deflecting apparatus IIO likewise receives its control signals from the output of the second detector.

with reference to Figure 5, the deflecting apparatuses I08 and I III are very similar to that described for the transmitter. The apparatus I00, for horizontal deflection at the receiver, comprises a condenser II I charged through a variable resistance II2 from a positive potential source as indicated. By adiustingthe switches H3 and H4 other condensers I I and I I0 may be charged through resistances I I1 and I I0 respectively from a high positive potential source to supply different predetermined li'ne frequencies for horizontal deflection. Charging current control may be obtained by varying the resistance through movable contacts I I3, I20 or I2I, to give close frequency adjustments.

When the voltage across condensers III, or I I0 or 0, depending upon which switch contacts are used, builds up, the saw tooth voltage waves in the plate circuit of tube I22 are impressed on the grid I23 of double purpose tube I24 through a voltage dividing resistance with a slidable contact I20 for controlling the amplitude of the saw tooth voltage waves. The output of the push-pull ampllfler tube I24 is applied to the load resistance I20 and I21 to change the potential on the horizontal deflecting plates I28 and I20 of tube I01 to effect the forward movement of the cathode ray.

To initiate the discharge of condensers III, I I0 or H0 in the absence of signal I provide an auxiliary scanning device or cathode ray tube I30 of conventional type and exactly like tube 30 previously described, and may comprise a fluorescence screen I3I of rectangular shape, one

set of electrostatic plates I32 and I33, multipled to the plates I28 and I28 respectively, and a small photoelectric cell I34 in a small glass tube near one edge of the screen. A separate set of feeders to the deflecting plates I32 and I33 may be provided, if it is desired to shift the center of the lines scanned on the screen.

When the cathode ray of tub I30 reaches the photocell I34, the change of light in this cell, due to the fluorescence material, will cause a voltage pulse to be applied to the grid I30 of tube I30 after suitable amplification and a phase reversal in tube I33 the signal is applied to the grid of the trigger tube I22 through resistance I31. This tube then becomes conductive to discharg either of the condensers III, H0 or H0.

to increase and decrease the potential on the vertical deflecting plates I08 and I00 of tube I01 to effect the vertical movement of the electron ray.

To initiate the discharge of condenser I30, I42 or I43 in the absence of control signals I provide an auxiliary scanning device or cathode ray tube I01 of conventional type and exactly like the tube I30 described above, having a screen I00 and a photoelectric cell I08. The plates I00 and III are multipled to the plates I00 and I00 so that the vertical movement across their respective screens will be in synchronism.

When the cathode ray of tube I01 is deflected until it strikes the photocell I00, the change of light on th photocell will cause a voltage wave to be applied to the grid I02 of the double triode I03; after suitable amplification and a phase reversal in tube I03, the signal is applied through resistance I04 to grid I00 of the trigger tube I40. The tube I43 then becomes conductive to discharge one of the connected condensers I00, I42 or I43.

From the foregoing, it will be understood that in the absence of signals, due to fading, or in turning the receiver on where there isgno transmitter operating, that the cathode ray will oscillate both horizontally and vertically.

The tube I01, Figure 4, may have on one side and on the bottom of the screen metal strips I01 and I08 with'separate leads brought out through the glass envelope. The strip I01 may be connected to the horizontal apparatus at I00, re-

placing the photocell I34, and the strip I00 may With further-reference to Figure 5, the vertical deflecting apparatus H0 is very similar to the horizontal deflecting apparatus and comprises a condenser I38, charged through a variable resistance I38 from a positive potential source as indicated. By rotating the switches I40 and HI other condensers I42 and I43 may be charged through resistances I44 and I40 from a positive potential source to thereby supply different predetermined frame or picture frequencies. Charging current control may also be obtained by varying the resistance through movable contacts I48, I41, or I48 to give close frame frequency adjustments.

When the voltage, across any one of the condensers I38, I42 or I43, builds up the saw tooth wave in the plate circuit of tube I40, is impressed on the grid I00 of tube IOI through the resistance and movable contact I02 for controlling the amplitud of the saw tooth voltage wave. The output of the push-pull amplifier tube IOI is applied to'the load resistances. I03 and I04 be connected to the vertical deflecting apparatus at I10, replacing the photocell I03.

The operation is as follows: The electron ray is deflected to impinge the plat I01 at the end of each line and to impinge the plate I00 at the end of each field to impress an F. on the grids of the tubes I30 and I03 respectively, which will operate the horizontal and vertical deflecting apparatus as described above.

The tube I01 may have the photocells I34 and I00 placed inside the envelope, close to the outer edges of the screen and as illustrated for the plates I01 and I08. The operation would be the same as above described.

The videoand control signals are demodulated at the second detector or rectifying tube I 00 and applied to the power amplifier I00, and after suitable amplification in the power amplifier I00 they are applied to. the control grid of the viewing tube I01. since the control or synchronizing signals are of a higher amplitude than the picture signals and appear at the end of each line and at the end 01 each field, they may be used to blank or reduce the intensity of the oathode ray in the viewing tube during the retrace period. 1

The video and control signals from detecto tube I00 are also applied to the grids of tubes I09 and I10. The tube I03 for controlling the horizontal deflection period is biased so that the picture signals will not produce plate current, but it does respond to both the line and field synchronizing pulses to thereby apply a voltage impulse through the coupling condenser "I to the grid I12 of tube I30. After suitable ampliflcation in its plate circuit the signal is applied to the trigger tube I22 to operate the horizontal deflecting apparatus, as previously described, to returintthe electron ray of tube I01 to its starting po 11 The tube I10 is biased to eliminate both the picture signals and the horizontal synchronizing impulses, but it will resp nd to the high amplitude field synchronizing pulse to impress a potential impulse through coupling condenser I13 to the grid I14 of tube I81. This tube will function as previously described to return the cathode ray to the starting point of the next field.

From the foregoing it is to be understood that the cathode ray inthe viewing tube will be returned either to its horizontal or horizontal and vertical starting point from any location on the screen upon the reception of a control or synchronizing signal. In other words, the horizontal control signals will return the electron beam to the starting point for the next line, and the vertical control signal will return the electron ray to the starting point of the first line in the next succeeding field.

The amplitude for thehorizontal and vertical deflection is adjusted by the movable contacts I25 and I! so that the ray will reach the photoaswps 1 I15 0! tube-I89 which would cause the horizontal deflecting. apparatus to function as before described. By the operation 01' switch IIlILtube I is rendered inoperative and the right plate circuit of tube I88 is supplied with positive. potential.

. The-blanking signals would also be applied to the second grid I18 of tube I88 after suitable amplification in its plate circuit the signal would be applied through coupling condenser I11 and the the grid I82, when the cathode ray impinges the photo cell I59. The vertical deflecting apparatus cells I and I59 or the metal plates I81 and I88,

reception of synchronizing signals, interposed between lines and between picture fields, the line deflecting apparatus will function upon the reception of the firsthorizontal control pulse to return the cathode ray to start the next line in synchronism with the transmitter. Upon the reception of the first vertical control puls the vertical deflecting apparatus will operate to return the electron ray to start the first line of the next succeeding field. Therefore the receiver will be automatically synchronized with the transmitter upon the reception of the first vertical synchronizing pulse, and the line deflection will be in step with the transmitter upon the reception of the first horizontal control pulse.

Synchronism is accomplished by transmitting a control pulse during each retrace period of the cathode ray in the pick up tube and utilizing this control pulse at the receiver to return the cathode ray in the viewing tube to the starting point of the next forward movement.

The devices I30 and I51 or'IBI and H58 may be considered primarily as safety devices So that} the cathode ray will continue to oscillate should the signals fade, or the transmittin station go oil the air. Withthe reception of strong signals these devices do not operate.

The receiver may be operated from any combination of lines and picture fields and diilerent transmitting stations may use difierent frequencies. The switches I I3 and I It for selecting horizontal frequencies and the switches I49 and MI for selecting vertical frequencies may be used to obtain the required frequency. The proper combination of resistance andcapacity should be used so that the cathode ray will be cut off just short of the safety devices I34 and 159 0r I61 and I68. The receiver running more slowly than the transmitter will cause the cathode ray to be returned before reaching the full size of the tube and the picture would be smaller than necessary.

The receiver may be used for monitoring on other television systems. By utilizing th blanking signals which are of higher amplitude than he picture signals, the blanking signals at end of will function as before described to returnthe cathode ray in the viewing tube IIl'I toits starting position.

From the foregoing it is to be understood that this receiver may be used for the reproduction 01 television signals from transmitters using various synchronizing methods.

In the various circuits shown and described I have simplified the drawings by indicating the source of potential by a positive or negative sign. Also I have omitted the heater filaments for the various tubes, but it will be understood that such filaments would be necessary.

Theembodiments of the invention which have been given herein are illustrations of how the 1 various features may be accomplished and of the principles involved. It isto be understood that the invention contained herein is capable of embodiment in many other forms and adaptations, without departing from the spirit of the invention and the scope of the appended claims.

Having thus described my invention, I claim: 1. In a television system, a cathode ray camera tube having an image plate and an electron ray directed toward the image plate, means for moving the said electron ray in forward and backward directions to scan said image plate, an auxiliary scanning device, means including said device for initiating the backward movement of the said electron ray and for controlling its intensity during its backward movement. 4

2. In a television system, a cathode ray can era tube having an image plate and an electron ray directed toward the image plate, means for moving the said electron ray in forward and backward directions to scan said image plate, means for developing picture signals during the forward movement of said ray, an auxiliary scanning device, means including said device for developing control signals, means associated with said tube responsive to the said control signals for initiating the backward movement of the said electron ray, and means fortransmitting the said picture signals and the said control signals alternately.

a 3. In a television system, a cathode ray camera tube having an image plate and an electron ray directed toward the image plate, means for moving the said electron ray in vertical directions, forward during'field periods and backwards during vertical retrace, means for moving the said electron ray in horizontal directions, forward to scan line locations on said image plate during said field periods, and backwards during line retrace, a. horizontal auxiliary scanning device, means including said device for initiating the backward horizontal movement of the said electron ray, a vertical auxiliary scanning device, and

each linewould supply a voltage wave to the'grid means including the said vertical scanning devicelfor initiating the backward vertical movementof the said electron ray.

"8.The'system.inaccordsncewithclaimli,in

- which there is provided means to vary the num- 4. In a television system, a cathode ray camera tube having an image plateand an electron ray directed toward the image plate, means for moving the said electron ray in vertical directions, forward during field periods and backwards during vertical retrace, means for moving the said electron ray in horizontal directions, forward to 'scan line locations on said image plate during saidfleld periods, and backwards'during line retrace, a horizontal auxiliary scanning device,

ber of line locations that may be scanned on the said image screen during the said field periods" and to change the intervals between the said horizontal synchronizingsignals. j I

9. The system, in accordance with claim 5, in which there is provided means to vary the number of image fields, that may be scanned in a given time, and to change the periodicity of the said vertical synchronizing signals.

means including said device 'for initiating the zontal directions to'scan saidimage screen. means tical synchronizing signals, means for moving the said electron ray in horizontal directions, forward to scan line locations on said image plate during said field periods, and backwards during line retrace, a horizontal control device, means including said horizontal control device-for developing horizontal synchronizing signals, means responsive to the said horizontal synchronizing signals for,

initiating the backward horizontal movement of said electron ray, and for controlling its intensity 10. In a television system, a cathode ray tube having; an image screen and 'an electron ray directed toward the image screen,""defiectlng means for moving said electron ray in vertical and horifor intercepting incoming horizontal and'vertical synchronizing impulses having unequally spaced vperiods, means for utilizing said horizontal impulses to initiate backward horizontal movements of said electron ray from substantially a mid portion of said screen and from one edge of said screen, and means actuated by said vertical im-y pulses to simultaneously initiate a vertical backward movement and horizontal backward movement of the electron ray. a

' 11. The system, in accordance with claim 10, in

which there is providedmeans actuated by the said deflecting means for initiating the backward during its backward movement, means responsive to the said vertical synchronizing signals for initiating both the vertical and horizontal backward movements of the said electron ray, means for developing picture signals during the forward horizontal movement of the said electron ray, and

and the said horizontal synchronizing signals alternately; and for transmitting the vertical sy chronizing signal at the end of each field-period."

6. In a television system, a cathode ray tube having an image screen and an electron ray directed toward the image screen, vertical deflecting means for controlling the movement of said electron ray in vertical directions during field periods, horizontal deflecting means including line signals for controlling the movement of said electron ray in horizontal reciprocating directions to successively scan line locations on said image screen. and means for returning. the electron ray to its starting point from substantially the midpoint of the first line in alternate field periods under the movement of the said electron ray in the absence of synchronizing impulses.

12. In a television system, a cathode ray tube havingan image screen and an electron ray directed toward the image screen, vertical deflecting means for moving the said electron ray forward vertically during field periods of time and back- I ward vertically during retrace, horizontal deflecting means for moving the said electron ray for ward horizontally to successively scan line locations on said image screen during field periods, and backward horizontally'during' retrace, meansfor intercepting incoming vertical synchronizing means for transmitting the said picture signals,

impulses and horizontal synchronizing impulses. suitable circuits and apparatuses for utilizing said vertical synchronizing impulses to cause the vertical deflecting means and the horizontal deflecting means to reverse the movements of the said control of said line signals, to thereby scan even line locations on said image screen during alternate field periods. I 7. In a television system, a cathode ray tube having an image screen and an electron ray directed toward the image screen, vertical deflecting means for controlling the movement of said electron ray in vertical directions during field periods,

horizontal deflecting means for controlling the electron ray both vertically and horizontally, certain of said circuits and apparatuses responsive to the backward horizontal movements of the said electron ray upon reaching one side of said screen and from a mid-location'on said screen to cause the electron ray to scan lines in one field diflerent than the lines scanned in the previous field. 13. Thesystem, in accordance with claim 12, in which there is provided switching means for varying the number of line locations scanned during field periods, and switching means for changing the number of field periods in a given time.

14. In a television system, a, cathode ray tube having an image screen and an electron ray directed toward the image screen, vertical deflecting means for moving the said electron ray forward vertically during fleld periods of time and backward vertically during retrace, horizontal deflecting means for moving the said electron ray forward horizontally to successively scan line 10- cations on said image screen during field periods, and backward horizontally during retrace, means for intercepting picture signals and control impulses alternately, apparatuses and suitable circuits for utilizing the said control impulses to cause the horizontal deflecting means to reverse between interception of the said picture signals and from intermediate positions on said screen 7 in certain recurring field periods, means for iden- .tifying and redeveloping one of said control impulses at the end of each image field and to apply the redeveloped impulses to other apparatuses of said ray, and means responsive to certain of the said linecontrol signals for causing the electron rayto scan different line locations on said image plate in alternate and intermediate-fields.

20. In a television transmitter, means for developing picture signals during relatively short and relatively long spaced periods of time, means and associated circuits to cause the vertical deflectingmeans to initiate the backward vertical movement of the said electron ray.

. lama television transmitter for modulating a carrier wave with control signals, a cathode ray camera tube having a mosaic image plate and an electron ray directed toward the image plate, means for moving the said electron ray in forward and backward directions to scan line locations on said image plate in successive fields, means driven by said first means for developing said control signals to modulate said carrier wave and to initiate the backwardmovement of said ray, and means responsive to certain of said control signals for causing the electron ray to scan different line locations on said image screen in alternate and intermediate fields. Y

16. In a television transmitter for modulating a carrier wave with signaling impulses, a cathode having an image plate and an electron ray directed, toward the image plate, deflecting means for moving the said electron ray forward during trace periods to scan line locations on said plate in successive fields and backward during retrace periods, means for developing picture signals during trace periods, means controlled by said deflecting means for developing signalling impulses at end of each trace period to modulate said carrier wave, means responsive to said impulses for initiating the retrace periods, and means responsive to certain of said impulses for causing the electron ray to scan different line 10- cations on said image screen in alternate and in- 17. In a television transmitter, a cathode ray camera tube having an image plate and an electron ray directed toward the image plate, a signalling device for producing signalling impulses, comprising a cathode ray tube having a target with a photo electric cell at one end of the target and an electron ray directed toward the target, means for moving both of said rays forward in unisonto scan the said image plate in the camera tube, and to increase the intensity of light on the said photo electric cell in the said device, to thereby produce a signalling impulse for initiating the backward movement of both of the said rays.

18. Ina television transmitter, a line and frame scanningdevice, means for producing picture signals during recurring line trace periods, and means operating in unison with the said device for producing scanning control impulses in the interval between line trace periods, one impulse for each interval to control the line scanning actions and the last control impulse in each frame to also control the frame scanning actions in the said scanning device.

19. 111 a television transmitter, a cathode ray camera tube having a mosaic image plate and an electron ray directed toward the image plate, means for moving the said electron ray forward and backward horizontally, and forward and backward vertically to scan line locations on the said image plate in successive fields, means for developing line control signals to initiate the horizontal backward movement of said ray, means for developing frame control signals to initiate both the vertical and horizontal backward movements for-developing a line or a combined line and frame control signal during each interval between said periods with a relatively short period appearing after each alternate combined signal, said line control signals occurring a greater number of times per second than the combined line and frame control signals, and means for transmitting the said picture signals and the said control signals alternately. a

21. In a television system, a cathode ray camera tube having an image plate and an electron ray directed toward the image plate, means for moving the said electron ray forward and backward horizontally, and forward and backward vertically to scan line locations in successive fields on the said image plate, means for producing periodically recurring control signal impulses; each impulse to initiate the backward movement of said ray both vertically and horizontally, and means for causing the electron my to scan different line locations on said image plate in alterhate and intermediate fields.

22. In a television transmitter, a cathode ray tube having an image screen and an electron ray directed toward the image screen, means for moving the said electron ray forwardand backward horizontally to scan a line on said screen, means for moving the said electron ray forward and backward vertically during spaced periods of time to cause different lines to be scanned on said screen, means for causing said electron ray to scan odd and even lines on said screen in alternate and intermediate periods respectively, means for developing control signal impulses, and means for driving the electron ray backward to a common starting point on said screen for each picture frame under the control of said signals.

23. In a television transmitter, a cathode ray cameratube having an image plate and an electron ray directed toward the image plate, means for deflecting the said electron ray forward and backward horizontally, and forward and backward vertically to scan lines in successive fields on the said image plate, means driven by said deflecting means for producing vertical control impulses to initiate the backward movements of said ray both vertically and horizontally, means for developing line control impulses, and means responsive to certain of said line control impulses for causing the electron ray to scan difierent line locations on said image plate in alternate and intermediate fields.

24, In a television transmitter, a cathode ray camera tube having an image plate and an electron ray directed toward the image plate, means for deflecting the said electron ray forward and backward horizontally and forward and backward vertically to scan lines in successive fields on the said image plate, means driven by said deflecting means for producing horizontal and vertical control impulses to initiate the backward movements of said ray, the horizontal control impulses initiating the horizontal backward movement, and the vertical control impulses initiating both the ver- 8 aaoaeu diirerent from the lines scanned in the previous field.

25. In a television transmitter, a cathode ray camera tube having an image plate and an electron ray directed toward the image plate, means for deflecting the said electron ray forward and backward horizontally, and forward and backward vertically to scan lines in successive fields on the said image plate, means for producing control impulses, means associated with said tube responsive to the said control impulses for initiating the backward movement of said ray both vertically and horizontally, means for changing the frequency of occurrence of said impulses to change the number of fields in a given time, and means for causing the electron ra to scan odd and even lines on said image plate in alternate and intermediate fields respectively.

26. In a television transmitter, a cathode my camera tube having an image plate and an electron ray directed toward the image plate, means for deflecting the said electron ray forward horizontally. and forward vertically to scan the said image plate, means for producing relatively low, and relatively high amplitude control impulses, means for deflecting the electron ray backward horizontally under the control of said low amplitude impulses, and means for deflecting the electron ray backward both vertically and horizontally under the control of said high amplitude impulses.

27. In a television transmitter, a cathode ray camera tube having a screen and an electron ray directed toward the screen, means for deflecting the said ray in horizontal and vertical directions forward and backward to scan lines in successive fields on said screen, an impulse generator device controlled by said means for producing control impulses to initiate the horizontal backward movement of said ray. another impulse generator device controlled by said means'for producing other control impulses to initiate both the horizontal and vertical backward movements of said ray at the same time, means for causing the electron ray to scan lines on said screen in one field different from the lines scanned in the previous field, and means for adjusting the said first means to change the frequency of occurrences of said impulses to thereby change the number of forward and backward movements of the electron ray in a given time.

28. In a television transmitter, a cathode ray camera tube having a screen and an electron ray directed toward the screen, means for deflecting the said ray forward and backward to scan line ldcations on said screen, an impulse generator comprising a cathode ray tube having a screen with a light sensitive device at one end of the screen and an electron ray directed toward the screen, said deflecting means also for deflecting the electron ray in the said impulse generator tube in unison with the electron ray in the said camera tube to impinge the light sensitive device thereby producing control impulses, means responsive to said impulse for initiating the backward'movement of said rays, and means for ad justing the said deflecting means to change the interval of time required for the forward movement of said rays thereby changing the number of line locations scanned in a given time and also changing the frequency of occurrence of said impulses.

29. In a television transmitter, a cathode ray tube having an image screen and an electron ray directed toward the screen, an impulse generator comprising a cathode ray tube having a screen with a light sensitive device at one end of the screen and an electron ray dirccted toward the screen, means common to both tubes for deflecting both electron rays forward and backward across their respective screen in unison, said electron ray in the camera tube for scanning line locations on the said image screen, and the said electron ray in the impulse generator tube for impinging the said light sensitive device to thereby produce control impulses at the ending of each line at the edge of the said image screen, means responsive to the said impulses for initiating the backward movement of both of the rays, and means for adjusting the said deflecting means to change the interval of time required for the forward movement of both rays, thereby changing the number of line locations scanned in a given time and also changing the interval between successive impulses.

30. In a television transmitter, a cathode ra camera tube having an image screen and an electhe said impulse generator tube in unison with the electron ray in the said camera tube to impinge the light sensitive device thereby producing control impulses, means responsive to said impulses for initiating the backward movement of the said irays, and means for adjusting the said deflecting means to change the interval of time required for the frame periods thereby changing the number of frames scanned in a given time and also changing the interval between successive impulses,

31. In a television transmitter, a cathode ray tube having an image plate and an electron ray directed toward said plate, means for deflecting the said ray forward and backward to scan line locations on said screen, means for deflecting the said my forward and backward vertically to scan imageflelds, means for producing control impulses to initiate the vertical backward movement of the said ray, and means responsive to the said impulse for producing a second control impulse to initiate the horizontal backward movement of said ray at substantially the mid point of the first line in the image field.

32. In a television transmitter, a cathode ray tube having an image plate and an electron ray directed toward said plate, means for deflecting the said ray forward and backward to scan line locations on said screen, means for deflecting the said ray forward and backward vertically to scan image fields, means for producing control impulses to initiate the vertical backward movement of the said ray, a relay responsive to the said impulses to-close a pair of contacts during alternate field periods, and means responsive to the closing of the said contacts for producing a second control impulse to initiate the horizontal backward movement of said ray at substantially the mid point of the first line in alternate image fields.

33. In a television transmitter, acathode ray tube having an image plate and an electron ray directed toward said plate, means for deflecting the said ray forward and backward to scan line locations on said screen. means for deflecting the said ray forward and backward vertically to scan image fields. for producing control impulses to initiate the a movement of the said ray, and means responsive to the said inpulses ior initiating the hm'lzontal movement of said ray at substantially the mid point of the first line in the image field.

34. In a television transmitter, a cathode ray tube having an image screen and an electron ray directed toward the screen, means for deflecting the said ray Zorward and backward to scan line locations on said screen, means for deflecting the said ray forward and d vertically to scan image fields, means for producing control impulses to initiate the vertical backward movement of the said ray, means responsive to said control impulses for producing signalling impulses during alternate field periods and a device responsive to the said impulses to initiate the horizontal backward movement of the said ra at substantially the mid point of the first line in alternate image fields.

35.- In a television transmitter, a cathode ray tube having an image screen and an electron ray directed toward the screen, means for deflecting the said ray forward and backward to scan line locations onthe said screen, a scanning control device for producing control impulses to initiate the backward movement of said ray, means for deflecting the said ray forward and backward vertically to scan image fields, means for producing vertical control impulses to initiate the backward movement of the said ray both vertically and horizontally, means responsive to the said vertical control impulses for producing signalling impulses during alternate field periods, and means responsive to the said signalling impulses for returning thesaid ray from substantially the mid point of a line to the starting point for the next line.

36. The system in accordance with claim 35 in which there is provided means for utilizing the said control impulses to controlthe intensity of the said electron ray during its backward movement.

37. In a television transmitter, a cathode ray tube having an image screen and an electron ray 39. In a television receiver, a cathode ray tube having an image screen and an electron ray directed toward the screen, means for deflecting the said ray forward and backward horizontally and vertically to scan line locations in successive image fields, means for intercepting line and frame control means responsive to the said line control for stopping the line forward movementof said ray and for causing the lines in one field to be between the lines in the next succ field, and m responsive to each framecontrol signal ior stopping the line, and the frame forward movements of said ray.

40. In a television system, a transmimng station, a scanning device at said transmitting station, comprising a cathode ray tube having an image plate and an electron ray directed toward the plate, means for deflecting said ray both horizontally and vertically to scan lines in successive frames in said plate-,means for producing line,

and frame control signals, the line control signals iorreversing' the line scanning actions, and the frame control signals for reversing both frame and line scanning actions in the said device, means for transmitting-the said control signals, a receiving station, a scanning device at said receiving station comprising a cathode ray tube having an image screen and an electron ray directed toward the screen, means for deflecting said ray both horizontally and vertically to scan lines in successive frames on said screen, means responsive to received line control signal for reversing the line scanning actions from any advanced position, and means responsive to each receiving frame control signal ior reversing both the line and frame scanning actions in the scanning device at the said receiver station in unison with the scanning actions at the said transmitting station ii. In a television receiver, a cathode ray tube having an image screen and an electron ray directed toward the image screen, means for dedirected toward the screen, means for deflecting V the said ray forward and backward to scan line locations on the said screen, a scanning control device for producing control impulses to initiate the backward movement of said ray. means for deflecting the said ray forward and backward vertically to scan image fields, means for producing vertical control impulses to initiate the backw movement of the said ray both vertically and horizontally, means responsive to the said vertical control impulses for produ i impulses during-alternate field periods, means responsive to the said impulses for producing line control impulses to initiate the horizontal backward movement of said my from substantially the mid point 01! a e to the starting point for the next line, and cans for transmitting said line and vertical control impulses.

38. In a television receiver, a cathode ray tube having an image screen and an electron ray di-= rected toward the screen, means for deflecting the said ray forward and backward horizontally and vertically to scan lines in successive fields on said screen, means for intercepting line, and'frame control impulses, means responsive to the linefleeting said ray forward and backward horizont Lv and vertically to scan lines in successive fields on said screen, means for intercepting incoming horizontal, and vertical control signals, means responsive to the said horizontal signals for reversing the horizontal deflection of said ray and for causing the electron my to scan lines in one field different than the lines scanned in the previous field, and means actuated by the said vertical signals for reversing both the horizontal and vertical deflection oi said ray.

42. -In a television receiver, a cathode ray tube having an image. screen and an electron ray directed toward the screen, means for deflecting the said ray forward horizontally and vertically to scan said screen, means for intercepting incoming line and frame control signals, means for defiecting the electron ray backward at the end of each line and at least once from the mid position in a line in alternate fields under the control of said line signals, and means for driving the electron ray backward both vertically and horizontally under the control of said frame signals.

43. In a television receiver, a cathode ray tube having an image screen and an electron ray directed toward the screen, means for deflecting the said ray forward and backward horizontally and vertically to scan said screen, means for intercepting relatively low, and relatively high amplithe vertical and horizontal forward movements 7 of said ray.

- cally to scan lines on said screen to produce picture images from received picture signals, and means for deflecting the electron ray backward attheendofeachlineandat leastoncefrom the mid position in a line in alternate fields under the control of received line control impulses.

45. The method of transmitting pictures of a scene within the view of the transmitter comprising a line and frame scanning device for developing picture signals during line trace periods in reciprocating scanning actions. a generator for developing line and frame control signals, utilisescape:

trace Periods in reciprocating scanning actions, utilising the said line control signals to reverse line scanning actions after either a full trace period or substantially one half of a trace period, said half trace period causing said electron my to scan odd and even lines in alternate and intermediate frames respectively and utilizing the said me said line control signals to reverse line scan- I ning actions, and utilizing the frame control signals to reverse both line and frame scanning actions in said scanning device to transmit said control signals along with the said picture signals.

48. The method of producing picture images from received video signals. unequally spaced line, and line and frame control signals comprising a line and frame scanning device for developing picture images from said video signals during line line and frame control signals to reverse both the line and frame scanning actions.

47. The method of producing picture images from received video signals, unequally spaced line, and line and frame control signals comprising a line 'and frame scanning device for developing picture images from said video signals during line trace periods in reciprocating scanning actions, utilizing each line control signal received to reverse the line scanning action either at the edge of said screen 'or' at substantially the mid point of said screen. the mid point reversal causing said ray to scan odd and even lines in alternate and intermediate frames respectively, and utilizing each line and frame control signal received to reverse both line and frame scanning actions.

48. In a radio system, a radio station, a pair of generators at said station for producing two sets of saw tooth waves comprising a first means for producing control signals toqterminate the waves in one of said sets and a second means for producing other control signals to terminate the waves in both of said sets simultaneously.

JOHN H. HOMRIGHOUS. 

